1. Field of the Invention
The present invention relates to optimizing the functionality of two distinct communication protocols that are implemented in the same system. More specifically, the present invention relates to optimizing the functionality of Bluetooth and Wi-Fi (Wireless Fidelity) signals in a coexistence scheme.
2. Description of the Related Art
Both Wi-Fi (IEEE 802.11) and Bluetooth (IEEE 802.15) operate in the 2.4 GHz ISM (Industrial Scientific Medical) unlicensed band. Wi-Fi is used to create a WLAN (wireless local area network), and Bluetooth is used to create a WPAN (wireless personal area network). Wi-Fi divides the 2.4 GHz ISM band into 20 MHz channels, and a station and an access point use one of the 20 MHz channels to send control and data messages. Bluetooth divides the whole 2.4 GHz ISM band into 74 adjacent 1 MHz channels and uses a hopping sequence between these 1 MHz channels to reduce interference and to increase privacy. However, when both Wi-Fi and Bluetooth are used, the hopping sequence of Bluetooth causes Wi-Fi and Bluetooth signals to interfere with each other.
This interference causes data loss in both the Wi-Fi and Bluetooth channels and can even lead to a terminated link. This situation is exacerbated in a device that simultaneously uses both Bluetooth and Wi-Fi. An example of such a situation is using a Bluetooth headset to make a VoIP (voice over internet protocol) voice call over a WLAN using Wi-Fi. This interference has a more profound effect on link SCO (Synchronous Connection Operation) or eSCO (extended Synchronous Connection Operation) with dedicated channel and stricter timing requirements due to voice latency issues than links that can tolerate delays like A2DP (Advanced Audio Distribution Profile).
To handle this interference, the IEEE recommends that the device with the Wi-Fi and Bluetooth transceivers includes a control block provided between the Wi-Fi and Bluetooth transceivers. This control block then selects which one of the Wi-Fi and Bluetooth transceivers is to operate at a particular time and assigns a higher priority to all Bluetooth transmissions. However, in a VoIP voice call over Wi-Fi, the connection between the callers can easily be terminated if all Bluetooth transmissions are chosen over simultaneous Wi-Fi transmissions, especially at low signal strength.
Another proposed solution to the interference problem is for Bluetooth to use AFH (Adaptive Frequency Hopping), which can be used to limit Bluetooth to only using those channels that will not interfere with the channels being used by Wi-Fi. However, AFH can only be used when Bluetooth and Wi-Fi are each using separate antennas and when there is sufficient isolation between the separate antennas. Accordingly, AFH cannot be used to solve Wi-Fi and Bluetooth interference problems in a system where a single antenna is being used for both Wi-Fi and Bluetooth.
An example of a system including Wi-Fi and Bluetooth coexistence is described in U.S. Patent Application Publication 2006/0194538. In the system described in this publication, a controller is provided between a Wi-Fi transceiver and a Bluetooth transceiver. When data is simultaneously received from both of the Wi-Fi transceiver and the Bluetooth transceiver, the controller prioritizes Wi-Fi transmissions and aborts Bluetooth transmissions unless the Bluetooth transmission is a re-transmission. That is, the controller will prioritize Wi-Fi transmissions over original Bluetooth transmissions (a first attempt at transmitting a Bluetooth packet), but will prioritize Bluetooth re-transmissions (second and subsequent attempts at transmitting a Bluetooth packet) over Wi-Fi transmissions. However, because this system assigns higher priority to Wi-Fi transmissions except for Bluetooth retransmissions, this system has a problem in low RSSI areas where Wi-Fi packet times are longer in that Bluetooth transmissions cannot be communicated in these areas. Further, this system has a problem in that it requires that eSCO be used because eSCO includes retransmission, while regular SCO does not.
Accordingly, there is an as of yet unmet need in the art for a system that can reduce interference between Wi-Fi and Bluetooth without unnecessarily reducing the transmitting speed of either Wi-Fi or Bluetooth.